The railroad cars in the foreground are Treadwell double pot slag cars and were used to transport slag, a compound of different waste products from making steel, away from the blast furnace. The slag was poured into the cars hot and then transported to where it could be dumped. There is an excellent movie showing the operation of one of these cars on YouTube.
This is the final shot from my Bethlehem Steel series. I can only hope that I get another chance to see this incredible place. The beauty, the scale, and the function of this place are unparalleled by any other abandonment I have ever been to. I will remember my trips here for a long, long time.